DE1262338B - Color television receiver circuit for determining the switching phase of the test signal for operation in a color television system of the Secam type - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL

H04n

German KL: 21 al - 34/31

Number: 1262 338

File number: C 34729 VIII a / 21 al

Filing date: December 22, 1964

Opening day: March 7, 1968

The invention relates to a color television receiver for operation in a color television system of the Secam type, in which the color video signal contains a brightness signal and a subcarrier which, during the active part-picture duration, alternates with two color signals A 1 and A 2 and alternating with the line frequency during control periods, which are each contained in a vertical blanking interval, with two identification signals al and al alternating with the line frequency ίο is frequency-modulated, the identification signals al and al being equal to themselves for two different line periods and such that the difference αϊ-α2 im extending a line period has a single polarity, the selectively transferring the Färbsignale al and al during the active field period, as well as the selective transmission of the identification signals and a2 during the control periods synchronously al to the first state or the transmission side of the second state in order switch takes place, which changes its state regularly with the line frequency at least between the beginning of each control period and the beginning of the vertical blanking interval containing the following control period, with a receiving-side switch with two states, which has two signal inputs and two outputs and the signals A 1 and A1 distributed to the corresponding channels, each of which contains a frequency demodulator, with a video-frequency test channel which emits a test signal during the control periods which has a correct polarity if the state of the receiving-side switch corresponds to the state of the transmitting-side switch, and the opposite If it has the other, incorrect polarity, and with a control circuit for the receiving-side changeover switch, which contains a first arrangement and a correction arrangement which regularly effects the changes in the state of the receiving-side changeover switch at the rate of the line frequency t, whose input is connected to the test channel and whose output is connected to the input of the first arrangement, and which changes or does not change the regular sequence of changes in the state of the switch between the start times of two successive control periods, depending on whether the test signal is at the beginning of the first of these two control periods has the wrong or the correct polarity.

A color television system of the type specified corresponds to a particular embodiment of the Secam system that was the subject of an older pre-color television receiver circuit to determine the switching phase of the test signal for operation in a Secam-type color television system

Applicant:

Compagnie Franchise de Television,

Levallois, Seine (France)

Representative:

Dipl.-Ing. E. Prince, Dr. rer. nat. G. Hauser
and Dipl.-Ing. G. Leiser, patent attorneys,
8000 Munich-Pasing, Ernsbergerstr. iy

Named as inventor:

Dominique Brouard,

Claude Ragot, Levallois, Seine (France)

Claimed priority:

France of December 27, 1963 (958 621)

blow is. The one given in the older proposal Transmission of two identification signals and influencing the control of the receiving side Changeover switch ensured by a test signal derived from the identification signals that the Reception-side changeover switch always works in phase with the transmission-side changeover switch, so that each the alternately transmitted color signals always reaches the channel assigned to it. When switching of the receiver or after falling out of step, the correct phase position of the receiving side Changeover switch made after a field period at the latest.

According to the older proposal, either one or the other identification signal is used directly as the test signal taken to one of the outputs of the receiving-side switch, or the test signal is taken from an output of the matrix, to the outputs of the switch on the receiving side or to the outputs of the switch downstream color subcarrier demodulators is connected and the color value signals from the alternately transmitted color signals forms.

From this older proposal, the color television receiver according to the invention differs in that that the receiver has an auxiliary matrix with two

809 517/502

3 4

Contains inputs and an output, the two partial image sync signal (including the pre and inputs from the outputs of the two frequency post-satellite) reserved time, the following intermodulators are derived that the auxiliary matrix vallP '(ten lines) corresponds to the black level, is designed that during the control period it is divided by pulses with the line frequency or emits a signal of the form k (at - a 2) if it is 5, and the last interval P " (five lines) serves as the receiver-side switch in the same To- transmission of type signals, which are located by the stand as the transmitter-side switch, and the same pulses are interrupted and the rule in the other case a signal of the form - k (al - al), allow the circuits, for example where k is a constant of proportionality pre- linearity with the help of sawtooth-shaped signals, the correct sign is, and that the output of the io with regard to the color carrier if the control auxiliary matrix forms the test channel. period D chronologically with the second half (five lines)

The object of the invention is to improve the interval P ' together, as a result of which it is possible in this case of the control circuit of the receiver-side Um- example to alternate five switches one after the other. to transmit the following identification signals.

The design according to the invention of the color tele-15 The two identification signals are in the form of a visual receiver, which has the advantage that the output al = a, al - - a.

The test signal obtained from the auxiliary matrix is very wide. The signal α consists of a positive signal in

going from the influence of interfering signals is free. Shape of a right-angled trapezoid, on the one

The invention is described below with reference to the short stage with the zero level, which the drawing is described by way of example. It shows 20 horizontal blanking interval. In Fig. 2, Fig. 1 shows a time diagram to illustrate the two such successive signals al = a possible position of a control period inside, of which only one is transmitted at the same time of a vertical blanking interval, since the signals al and al ab-

F i g. 2 shows the diagram of an identification signal that is transmitted alternately. F i g. 3 the block diagram of an embodiment 25 The signals A 1 and A1 are transmitted on the transmitting side to one of the receivers according to the invention and their higher frequencies are predistorted.

F i g. 4 shows a modification of the circuit of FIG. 3. thrown; this means that by an arrangement It should be remembered that in the case of a sequential filter, for example, a filter whose attenuation-simultaneous system is stored with a carrier-out frequency characteristic curve that increases with the frequency which is on the one hand with a brightness 30 function.

signal is modulated and on the other hand with a color known this measure brings a carrier, which in turn is alternately frequency-modulated with two with the broadening of the change interval of the signal with line frequency alternating color signals A 1 and, which depends on the form of the signal, Al, their Bandwidth, which can be limited if necessary, than that of the brightness signal. 35 for example with the help of a double limiter,

The invention is exemplary for the case, however, care should be taken that by this described that on the transmission side the following double limitation no impermissible distortions Conditions apply: be introduced (as these are not on the receiving end

The carrier is amplitude modulated and the color is compensated).

carrier is frequency modulated; the transmitted brightness is the following combination of color signals / el (RY) and kl (BY), that from -1 to

value signals: +1 goes, is the change interval of the predistorted

Yw = 0.59 Gw + 0 30 Rw + 0 11 Bw signals, for example, on the interval -2 to +2

'' 'limited to which the entire frequency deviation «

where Gw, Rw and Bw assigns the interval from the sampling circles 45.

supplied and previously gamma-corrected color value - The identification signal a - a \ = -al becomes

signals for green, red and blue, respectively, and the signals then with a maximum level of the value 2 or A 1 and A1 are two signals which are chosen to be the color near 2. The transmission circuit can be designed proportionally to differential signals (RY) and (BY) so that only the image signals Λ \, Α 2 when the signals denoted by R, G, B and Y are 50 predistorted; one can also quite simply become the one that results from the signals Rw, Gw, Bw and Yw by the same low-pass filtering as identification signals as the image signals. The output channel of the switch on the transmitting side of the pre-proportionality coefficients are subject to distortion. In this case, will be through

£ ι - _ 1/0 70 and kl = 1/0 89 ^ ^e double limit the peak values of these signals

55 suppressed, which may exceed level 2 - since the sum of the coefficients of G, R and B exceed.

has the value 1 in the expression for Y , F i g also applies. 3 shows an embodiment of the circuit

Relationship: gene for the recovery of the ink carrier in a recipient

0 59 (Q - γ) -i- 0 30 (R - Y) + 0 11 (B - Y) - 0 catcher according to the previously specified sende- '/ jv. )>) · _{6o stringent} conditions with the inventive

It follows that (G- Y) is a linear combination of improvements.

from (RY) and from (BY) and accordingly. In the arrangement of FIG.

of A is 1 and A1 . In each vertical blanking interval of the receiver the color carrier and its output is a control period in such a way as the modulation spectrum, which, for example, according to the in the time diagram of FIG. 1 is shown: Outward amplitude demodulation of the brightness signal carrier visibly of the transmission of the signals with which it was separated.

Carrier is directly modulated, is B (seven and a half This input 34 feeds one around the time T,

Lines) which are delayed for the transmission of the complete reciprocal of the line deflection frequency

Channel 35 and a direct channel, which is indicated schematically by a simple connection.

This arrangement makes it possible to repeat the signals A1 and A 2 and to make them available at the same time, the delayed signals coming from the channel 35, which relate to the previously transmitted image line, are approximately equated with the signals which relate to the currently in the Refer to the image line currently being transferred.

The outputs of the direct channel and the delayed channel feed the two inputs of a double changeover switch 367, which has the task of directing the signals A 1 and the corresponding delayed signals to a first output, which is connected to a frequency demodulator 38, and the signals A. 2 and to route the corresponding delayed signals to its second output, which is connected to a frequency demodulator 39. The changeover switch 367 also has two control inputs 47 ao and 48.

Since the factor kl of the signal Al = kl (RY) is negative, the demodulator 38 is connected in such a way that it reverses the polarity of the demodulated signal, ie the signal -Al outputs the signal A with the same polarity as RY , while the demodulator 39 outputs the signal A 2 with the same polarity as BY delivers.

The signals emitted by the frequency demodulators 38 and 39 are subjected to an equalization in equalization filters 381 and 391, which equalization compensates for the predistortion on the transmission side. The signals -kl (RY) and k2 (BY) are practically restored at the output of this filter with the change intervals - 1 to +1,

The identification signals are, however, afflicted with distortions which differ depending on whether they have been pre-distorted or not, but the limiting thresholds of the trapezoids remain fixed at +2 or - 2.

The equalization filters 381 and 391 feed a matrix 40, which at their outputs 51, 52 and 53 during the active line duration (which corresponds to the transmission of the image signals) in the active Field duration the signals

R-Y = (-A l) / (- kl) = A l / kl, B - Y = A2 / k2 or G-Y

output, with the last signal being a linear combination of the other two signals. During the control periods, the outputs 51 and 52 accordingly supply the signals all kl and a2lk2, respectively. Of course, this only applies under the condition that the changeover switch on the receiving side has the correct phase, that is to say that it is in the same state as the changeover switch on the transmitting side. In the opposite case, the signal a2 / kl is obtained at output 51 and the signal al / kl at output 52 during the control periods.

Since then -kl and k2 are positive, while al is positive and α 2 is negative, the two outputs 51 and 52 deliver negative signals when the receiving-side switch is in the correct phase, and positive signals in the opposite case. In both cases these signals have a trapezoidal shape with an upper (or lower) step value.

From the expression (GY) as a function of (RY) and (BY) it follows that during the control periods the signal emitted by the output 53 always has the opposite sign to the signals emitted by the outputs 51 and 52. If the changeover switch on the receiving side is in the correct phase, only output 53 delivers a positive signal during the control periods.

In order to prevent this positive signal from being disruptive on the screen of the picture display tube Creates structures, a gate circuit 800 is added to the output 53, which is at its control input 801 in the course of the vertical blanking intervals, at least during the transmission of the identification signals receives a lock signal that is slightly different from the deflection signals for the electron beams the three-color tube can be derived.

No gate circuit is arranged at the outputs 51 and 52, since this is the case with the correct phase of the Reception-side switch emit negative signals during the control periods, which are harmless because they increase the blocking of the electron beams, while one can neglect what happens when the receiving-side changeover switch is not in phase with the sending-side changeover switch because this case occurs only very rarely and then only very briefly.

The outputs 51 and 52 of the matrix 40 and the output of the gate circuit 800 are each connected to the Input of one of three amplifiers 701, 702 or 703 connected to output 704, 705 or 706.

The signals RY, GY and BY picked up at these outputs are used together with the brightness signal Y in a manner known per se for image reproduction.

The improvement according to the invention with regard to the formation of the test signal will now be described will.

The test signal is not, as is usual, at the output channel of one of the equalization filters 381 and 391 or the matrix 40, but at the output of an auxiliary matrix 802 with two inputs, which are connected to the outputs of the amplifiers 701 and 702.

This matrix thus receives input signals Ql and β2 during the control periods, which have the following values when the switch on the receiving side is in the correct phase:

Ql = allkl, Q2 = a2lk2,
and in the opposite case the values

Q2 - allcl.

In these expressions the common factor resulting from the same is disregarded Gain of amplifiers 701 and 702 results.

The parameters of the matrix 802 are dimensioned in such a way that they follow with their input signals Operation performs:

Q = kl-Ql-k2Q2.

If the phase of the switch on the receiving side is correct, the following applies:

Q = al - a2 = 2a (positive),
and in the opposite case:

Q = a2 - a1 = -2a (negative).

262 338

In both cases, the signals Q are trapezoidal signals, the steps of which have a high level in absolute terms with respect to the highest levels of the image signals At-A 2 and A2-A1 formed by the matrix §02 during the transmission of the image signals .

The output signal of the matrix 802 is the same as the signal, except for the amplification of the amplifiers would be obtained if the output from the outputs 51

Output signals of the equalizing filters 381 and 391 are supplied with reversal of sign; Then it will be immediately receive the following signal:

or

. - al = la

al - al = - 2a,

depending on whether the phase of the switch on the receiving side is correct or incorrect. This addition circuit would be replaced by a subtraction circuit if kl and kl were both positive, da

703 does not transmit the DC component.

In this case, they are followed by orders which restore this DC component.

If it is easy to restore the DC component, it can obviously that of the matrix io remove the matrix 802 signals to be supplied at the output of these arrangements and Sl 40 signals supplied in the.

Equal proportions would be combined, but it is Normally these arrangements are but one

Obviously advantageous to use the amplification of the organs to regulate the operation of the three-color amplifiers 701 and 702. associated with a tube, with this regulation a will-Except for a gain factor, the same arbitrary change in the DC voltage component combination Q can also be implemented with the help of a matrix that consists of a simple and this change the operation of the switching addition circuit exists, the two inputs of which falsify the gene for processing the test signal.

One solution is that even if the amplifiers 701 and 702 do not transmit the DC component, the output signals this amplifier can be used to generate the test signal, but then a correction is made. In this case, the output signals of amplifiers 701 and 702 are during of the control periods are in reality not free from a DC voltage component, but with a "Wrong" DC voltage component afflicted, which originates from the previously scanned partial image. This "wrong" DC voltage component becomes

then none of the demodulators removed the sign of the 30 with the help of a high-pass filter. Modulation signal reverses. If the cut-off frequency is set correctly, this can

The advantage of this type of formation is that the filter eliminates the DC component Test signal delivering combination of the following: and yet the trapezoidal

If signals are transmitted at the input 34 of the circuit for Ausformigen, because, as shown in FIG. 1 evaluation of the color carrier an interfering component is recognizable in advance, which is the beginning of a vertical blanking process is, this interfering component also calls, especially at the beginning of the associated control particular if the time interval separating periods by a sinusoidal oscillation is considerably longer forms is, for example, by the carrier frequency than the duration of the control period. of a transmitter, two signals of opposite polar- In F i g. 3 it is assumed that the

ity which prevail in the output signal of the matrix 40 purified conditions, which is why the matrix 802 cancel each other. 802 a high-pass filter 803 of the type specified

The test signal obtained in this way is therefore connected downstream.

much safer than the test signal that is transmitted to a signal obtained at the output of the filter 803

only one of the outputs of the receiving-side Um- is then fed to a low-pass filter 301, whose switch or at a single one of the outputs of the 45 cutoff frequency is on the one hand dimensioned so low that Matrix 40 or at the output of a single one of the influence of the possibly in the output signal of the more strongly 701 to 703 is decreased. Matrix 802 still existing interfering components

This advantage of the combination remains intact, is eliminated, which on the other hand is eliminated one is high enough in the manner shown that the negative and positive output signals of the amplifiers 701 and 702 works. 50 peaks of the test signal provided by the matrix 802

That are transmitted from the output of the equalization filter 381 with sufficient amplitude, The output of the filter 301 is connected to the control

Division by -kl and one input of a gate circuit 302 connected in the matrix 802. This multiplication with kl. In the same way, the receives at its signal input 303 pulses with the line frequency supplied by the output of the equalization filter 391, preferably the horizontal pulses supplied by the AbSignal a division by it 2 in the matrix 40 and control circuits of the receiver.

A diode is preferably connected in series with the filters 803 and 301 in such a way that the input 304 of the gate circuit 302, only the signals of the incorrect polarity are allowed to pass.

The gate circuit 302 is connected in such a way that it is unlocked as long as the signal fed to its control input is above a level - V ₀ ; the span output signals of amplifiers 701 and 702 used 65 voltage - V ₀ , on the other hand, is dimensioned to be the value. -V ₀ when a negative test signal occurs

However, this additional benefit requires that it is achieved quickly, but when transferring the Take precaution when the amplifier 701 to image signals cannot be reached.

a multiplication by - / c2 in the matrix 802. The All of these operations maintain the compensation obtained at the output of the equalization filters.

The main advantage results from the specified combination. An added benefit that is that the test signal is obtained with a higher level is achieved by the fact that the

9 10

These two conditions are not incompatible, controlling the receiving-side switch with one

because the signals A 1 and A 2 are combined according to the pre-color blocking arrangement.

The explanations given after the rectification of the A color blocking arrangement is an arrangement

Absolute value cannot achieve any values that would at least allow the color channels to be blocked.

which effects the step values of the trapezoids α comparable to the active partial image duration when the

are. received broadcast a black and white television

Accordingly, the gate circuit 302 is always broadcast. In this case contains the video signal

open except when a negative test signal occurs. no color amplifier, and the output of the

If the gate is open, the matrix 802 will have essentially the value zero.

The pulses fed to input 303 are normally OK. This signal is activated during the control periods

through the gate circuit 302 and release them in the case of a color television broadcast

preferably via a high-pass filter 804, whose time intervals are used as a test signal with the value zero

Purpose explained later, the state changes are considered. It's not exactly zero, of course, but it is

a bistable flip-flop 65, which, for example, can only achieve small values, and this is all the more true

a bistable multivibrator with two more outputs for the output signal of the filter 301.

gen, whose output signals the two control In F i g. 4 are only those opposite to FIG. 3 from

inputs 47 and 48 of the switch 367 supplied changed parts shown,

will. Input 304 receives that from filter 301 from

If the test signal is negative, the output reaches F i g. 3 test signal delivered in the same way

output signal of the filter 301 quickly reaches the value - F ₀ , 20 as in the circuit of FIG. 3 is obtained with

whereby the gate circuit 302 is blocked, and the difference that the possibly in series with

following horizontal pulse, which is connected between two diodes inserted on top of each other in such a way that

other trapezoidal signals appear, the transmitted polarity is the "correct" polarity.

finds the gate closed. The toggle switch is shown at 101,

device 65 "skips" a change of state, and 25 preferably a Schmitt trigger. This tilting scarf

the changeover switch 367 is in the correct switching phase device delivers a signal at its output 112 whose

brought back so that the trapezoidal pulse, amplitude value from the state of the flip-flop

which depends on the one stopped by the gate circuit 302, and that as a variable bias voltage to the

Horizontal pulse follows, is positive. The time constants lock and unlock the color channel. These

th of the arrangement are dimensioned so that the 30 variable preload can for example

output signal of the filter 301 during an active each output of the receiving-side switch

Line duration, time interval between two horizontal lines, in particular to amplifiers or

blanking interval, above the value - F ₀ increases. Limiters, for example with transistors, which are in

The purpose of the high pass filter 804 included in the frequency demodulators 38 and 39

Circuit can optionally be indicated is 35 are,

the following: The two states of the flip-flop 101,

The correspondingly filtered test signal is used as the one for blocking or unblocking the color

Control signal for the gate circuit 302 used. They correspond to channels, are loaded with "0" or "1"

it is desirable that it does not affect the price.

output signal of the gate circuit 302 has. On the other hand, output 112 controls the toggle

High-pass filter 804 is a more complicated structure circuit 101 at the same time an arrangement 107, the one

the gate circuit avoided for this purpose. The impulse emits then and only when the tilting

Test signal contains namely after the passage circuit 101 from the state "1" to the state "0"

through the filter 301 no more high frequencies. goes.

The high-pass filter 804 can therefore be dimensioned in this way. An adder 108 contains two inputs, from

that the control signal of the gate circuit through which the one input 303 the pulses with the

this cannot penetrate, while another line frequency, for example that of the receiver

on the other hand receives the short pulses with the line frequency delivered horizontal pulses, the to

be let through. are intended, usually the bistable toggle

In addition to this circuit, the two 50 circuit 65 (FIG. 3) can be switched with this frequency.

the following remarks can be made: touch.

λ T ^ - »* ·« «" 1, λ j η These are the impulses with the

1. The matrix 802 can be sized to _{line frequency, we} lche g in the circuit of F i. 3

the test signal, if desired no _ negative sent to _the signal input 303 of the gate circuit 302

Polantat, but a positive polarity in the _lead ^^ _{For this reason, the} ^s * _{it egg} ⁵

Incorrect switching phase of the receiving side of _the circuit is also referred to here with 303

Switch has. For this purpose, it is sufficient to _The ^ * & ^ _{lg2 Anord 108}

that they are connected _{to the A of} the arrangement 107 with the input signals

Operation performed: _{is> enabled e} ^B _{S; the one} generated by this arrangement - Q = - kl-Ql + k2-Q2. 60th impulses in the regular sequence of the line

o tv λ TJ u new o (w AA τ · τ to insert return pulses.

«JT Swif ^e ΐ and the low ^ _{A of the arrangement 108 is with the} pass filter 301 existing arrangement can be _{controlled by} * | _The toggle switch 65 (FIG. 3) combines appropriately sized bandpass filters

are set. _{6s The arrangement for} controlling the toggle switch

F i g. 4 shows a modification of the invention 101 contains a gate circuit 202, the control input

according to the receiver circuit, in which the input is the aforementioned input 304 and its

In order to establish phase synchronization, the signal input is fed as follows:

The vertical pulses, which are obtained in the same way as the previously mentioned pulses with the line frequency in the deflection circuits of the receiver, are fed to the input 143 of a differentiating circuit 142 which, for each vertical pulse, outputs a pulse pair / 1 and / 0 of opposite polarity which corresponds to the Correspond to the beginning and the end of the vertical pulse. The pulse / 1 occurs during section A (FIG. 1) of the portion of the vertical blanking interval preceding the control period and thus the test signal, while the pulse / 0 occurs when the test signal is present. These conditions are consistent with the timing diagram of FIG. 1 and can always be fulfilled with the aid of a suitable delay arrangement, which, for example, delays the test signal or the pair of pulses 71, / 0 so that the pulse / 1 occurs at the inputs of the gate circuit 202 before the test signal, while the pulse 70 occurs during the duration of the test signal appears, preferably closer to the end than to the beginning of this signal.

When these pulses 71 and 70 pass through gate 202, they become sequential the color blocking flip-flop circuit 101 is preferably supplied through a high-pass filter 204, which is the same Task like filter 804 in the circuit of FIG. 3 has.

The polarities and the amplitudes of the pulses 71 and 70 on the one hand and the flip-flop 101 on the other hand can always be dimensioned in such a way that the supply of the pulse 71 to the flip-flop 101 causes it to go into its state "1", which corresponds to the unlocking of the color channel, if it was not already in this state, and that the supply of the pulse 70 to the flip-flop circuit 101 changes it to its "0" state corresponding to the blocking of the color channels, if it did not already have this state. The corresponding correct polarities of the pulses 71 and 70 can in particular be obtained by supplying the vertical pulses to the differentiating circuit 142 with the corresponding polarity.

Gate 202, like gate 302 of the circuit of FIG. 3, is normal open minded. In contrast to the gate circuit 302, which only has been blocked for a test signal with incorrect polarity, it is only blocked for a test signal with locked with correct polarity.

Like the gate circuit 302, the gate circuit 202 is also dimensioned on the other hand so that the to their Blocking required voltage value can only be achieved during the control periods. One another solution with which the gate circuit 202 can be made more sensitive to the control signal, is that it is constructed so that it only applies to an input signal with the polarity of the pulse 70 can be unlocked.

In the course of each vertical blanking interval, the flip-flop circuit 101 is always by the pulse 71, which the Gate circuit 202 always finds open, returned to state "1" if it did not already have it.

It remains in this state if the test signal supplied by input 304 is sufficient Amplitude value and the correct polarity.

In this case, the gate circuit 202 is blocked when the pulse 70 occurs, which is therefore the toggle switch cannot achieve. This process is repeated in every vertical blanking interval, as long as the phase of the switch on the receiving side remains correct.

If the transmission received is a color television transmission, but the phase of the switch on the receiving side is incorrect during a control period, the pulse 70 reaches the flip-flop 101, which goes to the "0" state. The transition of the flip-flop 101 from the state "1" to the state "0" causes the generation of a pulse by the circuit 107. This circuit 107 can be formed by a differentiating circuit which is combined with a diode which is connected in such a way that it at the output of the arrangement 107 only allows the pulses with the corresponding polarity to appear.

The pulse thus supplied by the arrangement 107 is inserted in the adder 108 into the regular sequence of pulses which are fed to the input 303 of the adder at the line frequency.

The arrangement of FIG. 4 can always be set so that the additional pulse supplied by the arrangement 107 does not coincide in time with a pulse of the regular sequence. This is because this is possible because the toggle switch 101 can only go from the state “1” to the state “0” at a specific point in time of the vertical blanking intervals.

This additional pulse causes an additional toggle of the bistable flip-flop 65 and thus the establishment of phase synchronization of the changeover switch 367 (FIG. 3).

In the following control period you have returned to the first case, color television broadcast with the correct phase position of the receiving-side switch, and the color blocking toggle circuit 101 goes back to state "1", in which it remains in this case.

It should be noted that the described method entails a color blocking in the receiver, which is undesirable per se, for the duration of an active field duration, but it is of no practical importance since it occurs only sporadically and for about 1 second. It should also be noted that it would be the same to use a circuit 107 which supplies an additional pulse only when the flip-flop 101 goes from state "0" to state "1", with only a slight delay in the phase reset would, however, this delay would be negligible, and it would otherwise correspond to a time interval in which the color channel is blocked.

In the case of a black-and-white transmission or, more precisely, "color-free" transmission, the gate circuit 202 regularly lets the pulses 70 through, which causes the color blocking in the receiver during all active field intervals. The phase position of the switch on the receiving side is then irrelevant.

It can thus be seen that the in FIG. 4 is a very safe arrangement in which in the gate circuit 202 the effect of a test signal, which is largely insensitive to interference, is combined with a very precise and very safe auxiliary "signal with the field frequency (the pulses 70 and Jl) .

In contrast to the circuit of FIG. 3, apart from those connected to the outputs of the matrix 40

gates to be closed, continues the circuit described in FIG. 4 predict that

a) a control period is included in each vertical blanking interval,

b) the regular sequence of changes in the state of the changeover switch at the transmitting end does not become different Purposes during the part of the vertical blanking intervals preceding the control period is interrupted.

In particular, the arrangement can also be used when only a single identification signal a1 = α is transmitted. It is then sufficient to assume that the second identification signal «2 = 0.

On the other hand, the invention is also suitable for the case that the repetition of the signals after the Demodulation of the color carrier takes place.

It should be noted that the attenuation of the interference effects in the test signal does not apply to the case of a Noise signal of the simple structure given above is limited. It is sufficient that the interfering signal is from from one line period to the next does not change very much that its effects in this way are considerable be weakened.

Finally, the compensation also has an effect on the interference signals which are outside the control periods occur when the matrix for forming the test signal, as in the example given, is outside of the control periods remains coupled to the outputs of the switch on the receiving side.

Claims (4)

Patent claims: 1. A color television receiver for use in a color television system of the SECAM-type in which the color video signal includes a luminance signal and a color carrier alternately with two alternating with the line frequency during the active field period color signals Al and A2 and during control periods, each contained in a vertical blanking interval, with two of the line frequency alternating identification signals al al frequency modulated and in which the identification signals are al and al procure themselves the same and so for two different line periods that the difference has al -al during a line period a single polarity , whereby the optional transmission of the color signals A 1 and A 2 during the active field duration and the selective transmission of the identification signals al and al during the control periods takes place synchronously with the first state and the second state of a sender-side switch that has its state re changes regularly with the line frequency at least between the beginning of each control period and the beginning of the vertical blanking interval containing the following control period, with a receiving-side switch with two states which is arranged in the color channel and has two signal inputs and two outputs and signals A1 and A 2 to the corresponding channels distributed, each of which contains a frequency demodulator, with a video-frequency test channel that emits a test signal during the control periods that has a correct polarity if the state of the receiving-side switch corresponds to the state of the sending-side switch, and in the opposite case the other, incorrect polarity has, and with a control circuit for the receiving-side changeover switch, which contains a first arrangement causing the state changes of the receiving-side changeover switch regularly at the rate of the line frequency, and a correction arrangement, the input of which is connected to the test channel and d Its output is connected to the input of the first arrangement, and which changes or does not change the regular sequence of changes in the state of the changeover switch between the start times of two consecutive control periods, depending on whether the test signal at the beginning of the first of these two control periods is incorrect or correct Has polarity, characterized in that the receiver contains an auxiliary matrix (802) with two inputs and one output, the two inputs of which are derived from the outputs of the two frequency demodulators (38,39), that the auxiliary matrix (802) is designed so that it emits a signal of the form k {al-a 2) during the control periods if the receiving-side changeover switch (367) is in the same state as the transmitting-side changeover switch, and in the other case a signal of the form - Ic (al-a2), where k is a constant of proportionality with a predetermined sign, and that the output of the auxiliary matrix (802) includes test channel b educates. 2. Receiver according to claim 1 with two amplifiers, the inputs of which are coupled via the color matrix, the two equalization filters and the two frequency demodulators to the outputs of the receiving-side switch and during the active field duration in the event that the receiving-side switch is in the same state as the transmitter-side switch is located, emit signals that are proportional to the value A Hk 1 or A2 / k2, ie the color difference signals (R - Y) and (B - Y) , and where kl and k2 are proportionality constants with predetermined signs, characterized that the inputs of the auxiliary matrix (802) are coupled to the outputs of these amplifiers (704, 705). 3. Receiver according to claim 1 or 2, wherein the first arrangement of the control circuit for the receiving-side switch is formed by a transmission channel whose input is connected to an output of the synchronization and deflection circuits of the receiver, which emits pulses with the line frequency, and its output with the generator for the the receiving-side changeover switch is connected, and in which the correction arrangement is formed by a gate circuit which is inserted into the transmission channel is inserted, characterized in that the control input of the gate circuit (302) to the Output of the auxiliary matrix (802) preferably via a diode, which only the signals with the incorrect Polarity passes through, is coupled. 4. The receiver of claim 1 or 2, wherein the first arrangement of control circuitry for the receiving-side switch by a Transmission channel is formed, the input of which is connected to an output of the synchronizing and deflection circuits of the receiver is connected, which delivers pulses with the line frequency, 'and its output with the generator for the changeover switch on the receiving side Switching signals is coupled, and in which the correction arrangement is an addition circuit contains, one input of which is connected to the input of the transmission channel, and their Output is coupled to the output of the transmission channel, while the other input the addition circuit is connected to a correction pulse generator, the input of which is connected to the output of a color blocking toggle circuit, the output of the Color blocking toggle circuit on the other hand is coupled to the color channel in such a way that its detection Blocking or blocking is effected, depending on whether the toggle switch is in one or in the other of their states is, and the correction pulse generator each time then and only then delivers a pulse when the flip-flop switches from one predetermined state to the other State, characterized in that the control input of the color lock toggle circuit (101) is connected to the output of a gate circuit (202) whose signal input (305) has a Differentiation circuit (142) with a pulse at the field frequency supplying output of the Synchronization and deflection circuits of the receiver is connected and their control input (304) to the output of the auxiliary matrix (802), preferably via a diode, which only receives the signals passes with the correct polarity, is coupled. 1 sheet of drawings 809 517/502 2.68 © Bundesdruckerei Berlin